DESCRIPTION: Bioluminescence in Gonyaulax is derived from luciferase acting on its substrate luciferin in conjunction with luciferin binding protein (LBP). The result is rhythmic due to a rise and fall in LBP accomplished by translational control (the mRNA is constitutively synthesized. A region of the 3' end of LBP binds to a factor that is detectable in extracts only at night. The PI has determined the target sequence on LBP mRNA for the factor, and in the proposed studies will isolate and characterize the gene encoding it. The specific aims are to: (1) clone the LBP mRNA binding factor; (2) determine whether control of mRNA binding activity is due to cycling synthesis of the factor or circadian modification of a constitutively produced protein; and (3) establish the mechanism of translational control mediated by the protein's binding to LBP mRNA, and characterize possible interactions with both 3' and 5' regions of the target mRNA.